The Molecules of Cells Chapter Three

Classes of Compounds Organic compounds Inorganic compounds Carbohydrates, fats, proteins, nucleic acids Contain carbon, usually large, covalently bonded Inorganic compounds Water, salts, and many acids and bases Do not contain carbon Life’s molecular diversity is based on the properties of carbon

Characteristic chemical groups help determine the properties of organic compounds Functional Groups: affect a molecules function by participating in chemical reactions in a characteristic way

Cells make a huge number of large molecules from a small set of small molecules Most Macromolecules are Polymers Polymers: Large molecules consisting of many similar/identical building blocks linked by covalent bonds Monomers: Building blocks of polymers There are four classes of Biological Macromolecules (three are polymers): Carbohydrates Proteins Nucleic Acids Lipids (not polymers)

Polymers Around Us

Cells Make and Break Polymers Using Two Main Types of Chemical Reactions Dehydration (synthesis) reactions: Monomers are linked together to form polymers and a molecule of water is lost Each monomer contributes part of the H2O molecule that is lost

Cells Make and Break Polymers Using Two Main Types of Chemical Reactions Hydrolysis reactions: Polymers are broken down into monomers by the addition of water molecules reverse of the dehydration synthesis reactions

Carbohydrates Functions Major source of cellular fuel (glucose) Sugars and starches; polymers of monosaccharides Contain C, H, and O [(CH20)n] Three classes Monosaccharides -Simple sugars containing three to seven C atoms Disaccharides -Double sugars/too large to pass through cell membranes Polysaccharides -Polymers of simple sugars, e.g., starch, glycogen, cellulose Functions Major source of cellular fuel (glucose) Structural molecules (ribose sugar in RNA)

(a) Monosaccharides Monomers of carbohydrates Example Hexose sugars Example Pentose sugars Glucose Fructose Galactose Deoxyribose Ribose

(b) Disaccharides Consist of two linked monosaccharides Example Sucrose, maltose, and lactose Glucose Fructose Glucose Glucose Galactose Glucose Sucrose Maltose Lactose

Lipids Insoluble in water (hydrophobic) Contain C, H, O, sometimes P Several Classes of Lipids: Triglycerides Phospholipids Steroids

Triglycerides Triglycerides—solid fats and liquid oils Composed of three fatty acids and one glycerol molecule Main functions of TGs Energy storage Insulation Protection

Phospholipids Composed of two fatty acids, one glycerol and one phosphate group “Head” and “tail” regions have different properties Polar head, non-polar tail Main component of cellular membranes

Steroids Lipids composed of fused carbon ring structures Cholesterol, vitamin D, steroid hormones, and bile salts

Proteins Polymers of amino acids Contain C, H, O, N, sometimes S All 20 amino acids have same basic structure Amino acids are held together by special covalent bonds called peptide bonds https://www.youtube.com/watch?v=lijQ3a8yUYQ

Denaturing Natural Folding PRIMARY SECONDARY TERTIARY QUATERNARY https://www.youtube.com/watch?v=yZ2aY5lxEGE (protein folding animation 2m 19 s) start around 1:11 QUATERNARY

Nucleic Acids Polymers of nucleotides Contain C, O, H, N, and P A nucleotide consists of a nitrogen containing base, pentose sugar, and a phosphate group Contain C, O, H, N, and P Two types of Nucleic Acids: DNA and RNA

Deoxyribonucleic Acid (DNA) Contains four nitrogenous bases: adenine (A), guanine (G), cytosine (C) and thymine (T) Double-stranded, helical Replicates before cell division, ensuring genetic continuity Provides instructions for the synthesis of proteins

Ribonucleic Acid (RNA) Contains four nitrogenous bases: adenine (A), guanine (G), cytosine (C), and uracil (U) Contains uracil instead of thymine Single-stranded Mainly active outside of nucleus